Mine did that until I changed the control arm bushings. You might check them. I could get them to squeak if I rocked it side to side. I got someone to rock it while I got under and tracked down the problem. While it's rocking take a look at control arms, the sway bar connects and the rear track bar ends too. I have a 99 and have changed them all a few times so you maybe due. Hopefully it will not be the axle.
4" Teraflex long arm lift. D30 tubed with chromoly axles, high pinion, powertrax no-slip and Warn Lockout Hubs. D35 w/ultimate 35 upgrade OX locker, 4.56 gears. NP231HD, Air on Board, Warn M8000 Winch.